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Food Science & Nutrition > lips/triglycerides- week 3/4 > Flashcards

lips/triglycerides- week 3/4 Flashcards

(59 cards)

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1
Q

what is the melting point of a triglyceride based on

A

its dependent on its fatty acids & its crystal structure (polymorphism)

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2
Q

1) TG with high melting points are ………. at room temp.
2) TG with low melting points are ……. at room temp.

A

1) solid
2) liquid

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3
Q

when do fatty acids melt

A

occurs when intermolecular (van de waals) are broken
by heat energy (not intramolecular bonds)

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4
Q

what decreases the melting point of a fatty acid

A

increasing unsaturation
The more C=C bonds the lower the melting point

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5
Q

what increases the melting point of fatty acids

A

increases with chain length (number of carbons)
The longer the chain, the higher the melting point
Longer chains = more intermolecular bonds = more heat energy needed

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6
Q

how does the unsaturation of the fatty acid influence the melting point (2 points)

A

-trans C=C bonds introduce a slight kink and lower intermolecular bonds and thus less heat energy needed to melt
-cis C=C bonds introduce a larger kink (~42o
) and lower intermolecular bonds even more and thus even less
heat energy needed to melt

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7
Q

Triglycerides are polymorphic, what is it meant by polymorphic

A

means that TG can exist in more than one crystalline form

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8
Q

what are the three main polymorphic forms

A

α : alpha
β’ : Beta prime
β : Beta

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9
Q

what is the melting range of MP of fats dependent on

A

on the arrangement of TG molecules
i.e. their crystal structure

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10
Q

What are the properties of α-types (3 points)

A
  • Limited applications in foods and food processing (don’t form solids)
  • Randomly formed
  • Melts very easily
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11
Q

what are the properties of β’ -types (2 points)

A
  • Form small needle like crystals
  • Form soft plastic fats for use in margarine
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12
Q

what are the properties of β -types (3 points)

A
  • Form large crystals giving grainy texture (cocoa butter, lard)- too hard
  • Well ordered; hard texture
  • Not good for margarine
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13
Q

what is the definition of Tempering explain in terms of chocolate

A

controlled crystallization that is necessary to induce the desired form
of cocoa butter in the finished product (Used to Prepare Food with Desired
Polymorphic State of a Lipid)

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14
Q

what are the 3 states that lipids can exist depending on temperature

A

-solid (All TGs liquid)
-plastic (TGs with short chain FA liquid TGs with long chains solid)
-liquid (All TGs liquid)

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15
Q

Outline the difference between a simple and mixed triglyceride

A

In a simple triglyceride such as palmitin or stearin, all three fatty-acid groups are identical. In a mixed triglyceride, two or even three different fatty-acid groups are present; most fats and oils contain mixed triglycerides.

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16
Q

how is the process of tempering used to form chocolate

A

-Liquid cooled to initiate crystallisation
-Reheated to 32 degrees (just below the mpt of β-3 type) and
held – this melts out unwanted crystals
-Stir at 32 degrees, allow formation of very small β-3 crystals
and then finally solidify

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17
Q

what are the natural commodities lipids are obtained from (3 points and give examples of each)

A

-plants-
Oil Seeds (Rape, Sunflower, Palm Kernel, Soybean,
Cottonseed, Corn germ, Peanut, Coconut)
Fruit Pulp (Olive, Palm Fruit)
-animals & Fish-
* Lard (rendered from pig kidney fat, fatback, caul fat)
* Tallow (The rendered form of fat from sheep and cattle)
* Marine oils (Fish, Whales)
-Milk fats-
produced from churning whole milk or cream

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18
Q

Describe how lipids are purified from natural commodities from FRUIT (4 points)

A

-Grinding to a paste
-Pressing
-Separation (decantation or vertical centrifuge)
-Heating/Solvent Extraction

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19
Q

Describe how lipids are purified from natural commodities from seeds (5 points) - Milling

A

-Cleaning
-Breaking
-Cooking 70-100oC (to denature the enzymes like lipase & killing microbes)
-Expelling
-Solvent Extraction (hexane/heptane)

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20
Q

what are the 2 ways of Oil/Fat Extraction from Lipid-Rich Animals

A

wet rendering and dry rendering

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21
Q

what are the steps for wet rendering (5 steps)

A
  • Tissue heated with steam (high temp of about 100-110oC)
  • Lipid melts
  • Lipid separated by decanting or centrifugation
  • White lipid with neutral flavour, e.g., Lard
  • Process milder than dry rendering
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22
Q

what are the steps for dry rendering (4 steps)

A
  • Uses high heat alone
  • A harsher process than wet rendering
  • Browner lipid with stronger flavour
  • Non food uses e.g. soap
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23
Q

what are the 2 ways of refining oils

A
  • Caustic or chemical refining
  • Physical refining
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24
Q

what are the steps for caustic or chemical refining (6 steps + define each step)

Study These Flashcards
A

-Crude Lipid (TGs, water, protein, phospholipids)
-DEGUMMING (Removal of phospholipids + some protein)
-NEUTRALISATION (Removal of free fatty acids)
-BLEACHING (Removal of colour and pro-oxidants)
-DEODORISATION (Removal of volatile compounds and flavours)
-Crude Lipid (TGs, water, protein, phospholipids)
Refined Oil (one of the purest foods known)
Refining Steps in Detail
DEGUMMING
2-3% water added + agitation at ~50 degrees
Water phase removed after phase separation

25
what are the steps for physical refining (5 steps + explain each step)
-Crude Lipid (TGs, water, protein, phospholipids) -DEGUMMING (Removal of phospholipids + some protein) -STEAM DISTILLATION UNDER HIGH VACUUM (Removal of free fatty acids and deodorisation in one step) -BLEACHING (Removal of colour and pro-oxidants) -Refined Oil is produced
26
give in DETAIL the process of DEGUMMING in Caustic or Chemical Refining
2-3% water added + agitation at ~50 degrees Water phase removed after phase separation
27
give in DETAIL the process of NEUTRALISATION in Caustic or Chemical Refining
Caustic soda added to heated fat Aqueous solution (soap stock) removed; Washed with hot water
28
give in DETAIL the process of BLEACHING in Caustic or Chemical Refining
Heated to 85 degrees and absorbents added (Fullers earth or activated carbons); The bleaching earth removed by filtration
29
give in DETAIL the process of DEODOURISATION in Caustic or Chemical Refining
Steam distillation-steam passed through oil under reduced pressure Citric acid is often added to sequester metals
30
What is lipid modification
The alteration of one or more fatty acids in a lipid, resulting in a change in the properties of the lipid
31
Why are lipids modified (5 points)
Most of our food products is oil/ 75% of world edible oil is vegetable oil Melting point not suitable for processing Crystal structure not fit for production Cloudy when cooled Unstable (oxidation)
32
What are the 3 different methods of lipid modification
Hydrogenation Fractionation Interesterification
33
Explain hydrogenation (What does it do to FAs/what does it produce/characteristics of hydrogenated FAs)
-removed double carbon bonds- end up with trans fatty acids(increase HDL -means it increases the melting point -can convert cheap vegetable oils into plastic fats -improves stability -Generates hydrogenated vegetable oils (HVO)/trans fats
34
What is Interesterification/ what can it do to the lipid/ what's its properties
* Rearranges fatty acids on the glycerol backbone of TGs * Can change melting point * Can change crystal structure * Improves properties (more plastic) (Can change to what you what the product you want, and it doesn’t produce trans-fatty acids) *Converts cis bonds into trans double bonds
35
what are the importance of lipids in food
-Nutrition (essential FAs, e.g linoleic acids & lipids are essential of bilayers) -Palatability (flavour, texture, solubility) -Processing (heat transfer)
36
what are lipids
Compounds that are soluble in non polar solvents and are insoluble in water
37
what are the major classes lipids can be classified into
» Simple lipids (waxes, fatty acids, mono-, di-, triglycerides) » Compound lipids-structural lipids (phosphoglycerides, glycolipids- all are polar) » Derived lipids (sterols, fat soluble vitamins)
38
what is it meant by a lipid is polar
it has a hydrophobic tail and hydrophilic head
39
what is the structure of glyceride and how can you tell if its a simple or mixed triglyceride
glycerol + FA = triglyceride in the triglyceride has the SAME variable regions = SIMPLE if 2 are a least DIFFERENT it means its MIXED
40
what is the difference between a phosphoglyceride and a triglyceride
Similar to triglycerides (TGs) but are polar (eg. emulsifying agents
41
what is the structure of a phosphoglyceride
it has: -choline -glycerol -phosphate -Fatty Acid
42
what is a Fatty Acid
FAs are chains of carbon and hydrogen atoms with a terminal carboxyl group
43
How are saturated Fatty acids named
Named in accord with the number of C atoms including the COOH group i.e: CH3CH2 CH2 CH2 CH2COOH ----->HexANOIC (Caproic acid) CH3CH2 CH2COOH ButANOIC (Butyric acid) anoic -means its a saturated FA
44
in unsaturated fatty acids what are the 2 types of methylated double bonds
-Methylene interrupted -Conjugated (where this there is no CH2 in between the double bounds- Rare)
45
what is it meant by methylene interrupted
FA is interrupted by a CH2 in between the double bonds
46
what are the influence of TG structure in the nature/use of lipids
-Type of FA and arrangement responsible for the varied properties of TGs in foods ---->TG melting point is dependent on its fatty acids & its crystal structure (polymorphism)
47
give examples of lipid rich foods and the content of TG in them (4)
-Ruminant Milk Fat TGs * Short chain FAs (C4 -C12) + trans FAs -Vegetable Fat and Oil TGs * Seed oils-low in sat FAs * Vegetable fats, High sat/unsat ratio No fully saturated TGs - Animal Fats * Fully saturated TGs present; solid at room temp (20oC)- some unsat - Marine Oils * Low in saturated FAs; liquid at room temp * High in long chain polyunsaturated (PU) FAs
48
describe how the Fatty acid structure influence TG properties (3 points)
-Melting of fatty acids occurs when intermolecular (van de waals) are broken by heat energy (not intramolecular bonds) -Melting point increases with chain length (number of carbons) The longer the chain, the higher the melting point -Melting point decreases with increasing unsaturation The more C=C bonds the lower the melting point
49
what influence does the chain length have on the Melting point of FAs
Longer chains = more intermolecular bonds = more heat energy needed
50
rank in Oder from the highest MP to the lowest MP: TGs have C18 Saturated FAs TGs have C4-C12 Saturated FAs TGs have Unsaturated FAs
highest --->lowest MP TGs have C18 Saturated FAs (solid- e.g Lard) TGs have C4-C12 Saturated FAs (semi-solid- e.g butter) TGs have Unsaturated FAs (liquid- e.g oils)
51
define polymorphic and give an example of one
Triglycerides are polymorphic meaning they can exist in more than one crystalline form
52
what are the three main polymorphic forms
α - alpha β’ - beta prime β - beta
53
what causes the different polymorphic forms to form
The forms that grow depend on HOW the liquid is cooled
54
how does α-types affect the application of Lipids/ what's its characteristics
* Limited applications in foods and food processing * Randomly formed * Melts very easily
55
how does β’-types affect the application of Lipids/ what's its characteristics
* Form small needle like crystals * Form soft plastic fats for use in margarine
56
how does β-types affect the application of Lipids/ what's its characteristics
* Form large crystals giving grainy texture (cocoa butter, lard) * Well ordered; hard texture * Not good for margarine
57
define Tempering
Used to Prepare Food with Desired Polymorphic State of a Lipid---->controlled crystallization that is necessary to induce the desired form of cocoa butter in the finished product » This is the last stage in the process » Ensures that chocolate is in the correct crystalline state
58
Which polymorphic state exists in chocolates and margarine?
small β-3 crystals
59
what are the natural commodities lipids are derived from
-Plants: Oil SEEDS(i.e sunflower ,rapeseed, soybean) & fruit PULP (olive, palm fruit) - Animals & Fish: Lard (rendered from pig kidney fat), Tallow (The rendered form of fat from sheep and cattle), Marine oils -Milk fats: butter produced from churning whole milk or cream. *rendering =product that is melted in order to separate out the impurities.

Food Science & Nutrition (6 decks)

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